Parasite

Parasite is a science fiction novel written by Mira Grant (the pseudonym of American author Seanan McGuire). It was released on October 29, 2013, by Orbit Books and is the first volume of the Parasitology trilogy. The other two books in the series are Symbiont (November 25, 2014) and Chimera (November 24, 2015).The book envisages a world with fictional parasites, where people's immune systems are maintained by genetically engineered tapeworms.